This invention relates generally to the polishing of metallic surfaces, and more particularly, to a method and apparatus for polishing the stem of an internal combustion engine valve.
Internal combustion engine valves have a tendency to become fouled in use. When such fouling sufficiently reduces the performance, the valves are removed and refurbished. The refurbishment includes removal of carbon deposits by batch cleaning of the valves. Such cleaning process tends to impart minute deformities in the valve surface. The valve surface must be restored to a predetermined finish prior to installing in an engine. One known technique is to grind the valve stems. This involves the removal of material from the valve stem surface which requires that a valve guide insert be positioned in the valve guide to accommodate the reduced valve stem diameter. Such method requires the additional material and labor expense of installing the valve guide inserts.
A long felt need has existed for a technique for polishing valve stems. In contrast to grinding, polishing is not intended to alter the dimensions of the article. Rather, the surface is restored close to its original finish without a substantial removal of material. A successful technique for polishing valve stems, however, has proved to be elusive. While polishing is not intended to remove surface material, prior attempts at polishing valve stems have either produced an out-of-round condition of the stem or a non-uniform stem diameter.